Preheat the oven to 425°F (220°C). Place a baking sheet or Dutch oven inside to heat up.
Combine the sifted flour, baking soda, and salt in a large mixing bowl, stirring until evenly distributed.
4 cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon salt
Make a well in the center of the dry ingredients. Pour in the buttermilk gradually, stirring with a wooden spoon or spatula to form a soft, sticky dough.
1 1/2 cups buttermilk
Turn the dough out onto a lightly floured surface and gently knead it just enough to bring it together—about 4-5 turns. Shape into a round loaf approximately 8 inches in diameter.
4 cups all-purpose flour
Place the shaped dough onto a piece of parchment paper or a floured cloth, then use a sharp knife to score a deep X across the top.
Transfer the loaf onto the preheated baking sheet or into the Dutch oven. Bake for 40-45 minutes, until the crust is deep golden brown and the loaf sounds hollow when tapped on the bottom.